Turn knob switch with push-in terminals



Jan. 29, 1957 v. R. DESPARD TURN KNOB SWITCH WITH PUSH-IN TERMINALS Filed Sept. 27, 1954 ATTOR NEY$ United. States Patent 2,7 79,823 TURN KNOB SWITCH WITH PUSH-IN TERMINALS Victor R. Despard, Syracuse, N. Y., assignor to Pass & Seymour, Inc., Syracuse, N. Y., a corporation of New 'York Application September 27, 1954, Serial No. 458,563

11 Claims. (Cl. 200-6) his invention relates to switches and more particularly to the flush mounted type of switch with turn knob actuation and push-in, automatic wire gripping, terminals.

It is a general object of the present invention to provide a novel and improved switch of the type described.

An important object of the invention resides in the provision of switch contact and wire gripping units of unique form capable of simple, rigid mounting in the switch housing.

Another important object of the invention comprises the arrangement and shaping of the switch housing to accommodate the several sets of contact-terminal units to provide suitable operational characteristics within a minimum volume.

A further important object of the invention comprises the construction of the contact-terminal units and the housing for interlocking relation to insure rigidity of the operating parts in the housing together with means whereby the assembly is maintained and parts locked in position by the housing cover.

A still further important object of the invention resides in the use of spring-wing type wire gripping terminals which are open at one end together with positioning and aligning means for the free ends of the wings incorporated in and positioned by the housing.

A further important object of the invention consists in the symmetrical arrangement of the movable and stationary contacts and their wire gripping terminals facilitating wiring of the switch and permitting its assembly either as a commercially designated three-way or as a single-pole switch.

Other and further objects and features of the invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawings and following specification wherein is disclosed a single exemplary embodiment of the invention with the understanding that such changes and modifications may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.

In said drawings:

Fig. 1 is a side elevation of a turn knob wall switch with push-in terminals constructed in accordance with the present invention, the housing below the cover being sectioned on the plane indicated by line 11 of Fig. 2 to illustrate the arrangement and disposition of the terminals and contacts;

Fig. 2 is a top plan view of the switch with cover removed and the operating stem in section;

Fig. 3 is a transverse central vertical section taken on the plane indicated by line 3-3 of Fig. 1;

Fig. 4 is a transverse vertical section through the switch taken on the plane indicated by line 44 of Fig. l and passing centrally through one of the combined stationary contact and push-in wire grip terminal units;

Fig. 5 is a perspective View of the unit comprising the movable contacts, their spring arms and the wire grip terminal therefor; and

2,779,828 Patented Jan. 29, 1957 Fig. 6 is an elevation of the insulation sheet providing hold-downs for the terminals.

in applicants copending applications Serial No. 319,249 for A. C. Switch With Knob Actuation, now Patent 2,697,143, December 14, 1954, and Serial No. 245,l07 for Snap Switch With Oscillating Knob, now Patent 2,697,- 142, December 14, 1954, there have been disclosed construction of switches for mounting beneath wall plates in flush mounted house-type wiring wherein the switch has a turn knob rather than a tumbler lever or pushbutton for operation. Because of the relatively slow make and break of these switches their use is primarily restricted to alternating current circuits. They are not of the snap type and hence can be extremely silent without resorting to liquid contact or other costly construction. in the earlier disclosures the switch housings are constructed and arranged for selective insertion in mounting straps or bridges which may be fastened across the face of a switch or conduit box. The straps support from one to three switches or up to three wiring devices, one or more of which may be switches, in the space originally occupied by a single switch, i. e., in a so-called single gang box.

The present switch is illustrated as of the same general form but obviously is not so restricted in its mounting. The earlier switches made use of conventional form of screw terminals for attaching conducting wires to the contacts but it has been found that a great deal of the wirernans time can be saved by eliminating thi type of terminal which requires the stripping and looping of the ends of the conductors, their introduction beneath the screw head and the proper tightening of the. screw without causing the wire loo-p to be displaced beneath it. The present invention is, therefore, primarily directed to the provision of so-called push-in type terminals in switches of the general character disclosed in those aforementioned applications. in converting to the newer and faster automatic wire gripping devices economies are efi'ected in the use of metal and housing material and the total volume of the switch is considerably reduced facilitating the in troduction of a plurality of them and their many wires into a relatively small wall box.

For a better understanding of the invention, refeenc should be had to the accompanying drawing where illustrates the switch housing molded of a suitable plastic material generally rectangular in plane as seen in ig. 2 having generally flat side walls 11 and i2, and fiat end walls 13 and 14, and a bottom depressed at the center as shown at 15 and having two equal end areas 16 and 17 much closer to the open top of the housing.

The housing is closed by a molded insulation cover 18 held in position by a metal collar 19 having depending legs 21 expanded into grooves in the side walls in a known manner. The cover is provided with neck 22 adapted to be received in the mounting strap of the wall box and having a top portion 23 for projection through the face plate covering the switch.

The actuating knob and its parts are well described in the prior applications referred to above but it may be mentioned here that the projecting portion 25 of the knob is adapted to be grasped between the thumb and finger and rotated in one direction or the other for a part revolution to actuate the switch. The knob is journalled in a suitable opening in the housing cover and cooperating stops to limit the arc of movement are provided. An extending rod or stem 26 projects from the lower end of the knob and is journalled at 27 in a notch in the lower bottom wall 15 of the housing. This stem is provided with a crank arm 28 notched to receive a hairpin type spring so compressed between the lever and a groove 31 in the side wall 11 whereby the spring becomes an over center'type adapted to hold the lever in either of its two maximum extreme positions after it has passed over dead center by actuation of the knob 25. Depending lugs 32, 33 and 24 on the knob, seen in Figs. 1 and 3, serve to cooperate with one or more movable contact springs for actuating the switch in a manner which will subsequently appear.

The switch illustrated is of the commercially tilted three-way type, more properly described as a single-pole double-throw switch but obviously by the omission of one set of contact elements could be converted to a simple single-pole type.

The most important feature of the invention resides in the modification of the turn knob switch to accommodate automatic wire gripping devices adapted to seize and hold the bared ends of conductors when they are merely pushed through holes in the bottom wall of the housing. Each one of these terminals is incorporated into a unit with contact supporting mechanism for facilitating the assembly and positioning of the parts.

The movable contact assembly is shown in detail in Fig. and comprises a U-shaped strap spring having a flat base 40 and upstanding arms 41 each having on its outer face intermediate its length a contact button 42. The wire gripping device associated with this spring contact assembly comprises a sheet 43 of resilient metal having a portion underlying the base 40 of the contact springs, a pair of resilient connecting portions 44 spaced apart to provide the opening 45 and a pair of wire gripping wings 46 having their outer ends 47 free and their inner ends integral with the connecting portion 44. This assembly is adapted to be positioned in the lower chamber of the housing to bottom on portion of the bottom wall, and the outer edges 48 of the wings and connecting portions engage this bottom wall as clearly seen while the inner edges of the wings 46 are elevated from a pretwist given the parts 44 forming a channel-like tapered opening into which a wire end can be thrust to push the wings farther apart so that their inner edges, spaced apart less than the diameter of the smallest wire to be used, grasp the wire and because of their included angle prevent its withdrawal. The unit is fastened into the chamber in the bottom of the housing by a rivet 50 which connects spring portion 40 with plate 43 from which the wings are cut, and passes through an opening in the bottom of the housing to be headed over at 51, Fig. 3. This head may be covered with a suitable filling compound retained in place by the collar on the outer side of the bottom wall as seen.

The wings 46 have their edges 48 supported against lateral movement, so that they cannot spread when tension is applied to a wire inserted between them, by engagement with the side Walls 53 of the lower housing chamber. To prevent the wings from being drawn together sufiiciently to cut off a wire clamped between them when undue tension is placed on it, a buttress 54 is formed integral with the bottom wall 15 to engage and support the wings against collapsing any further than to the position shown in Fig. 1. This buttress isperforated by hole 55 extending clear through the bottom wall of the housing which permits the insertion of a wire to be connected to the switch. Its maximum diameter limits the size of the wire to that customarily used for the purpose.

It will be noted that when the wire gripping and contact spring assembly is in position the contacts 42 on the springs face the nearest end walls of the housing and are closely adjacent the side wall 11. In order that they may perform their desired functions they confront stationary contacts 56, one mounted on each of the unitary wire gripping and contact supporting assemblages 60, one of which is seated against each elevated portion of the bottom wall and adjacent eachend wall of the housing.

Each of these assemblies, except for the contact button, is a unitary structure struck out from resilient sheet metal to the form illustrated-in the drawings. Thus each of these units has a pair of wire gripping wings 61 similar to those defined in connection with the central wire gripping device, a pair of narrow resilient connecting arms 62, and a central opening 63, all forming part of the wire gripping portion most of which lies against the bottom wall of the housing as seen in Figs. 1, 2 and 4. The edges of the wings are prevented from spreading in a manner similar to that described in connection with the first-mentioned wire gripping device as by having lateral engagement with the end walls 13 and 14 as at 64 and with the integral upstanding studs 65 which are positioned closely adjacent the entrance to the lower chamber in the housing. To further facilitate positioning and stabilizing the assembly a molded stud 66 extends through each opening 63.

The metal sheet from which the wire gripping device is formed is bent upwardly at 68 beyond the opening 63 to lie along the side wall 11 of the housing, extending to its upper edge where the inturned portion 69 cooperates with the underface of the cover and a stud 70 thereon whereby the assembly is held in position in the housing against displacement under all normal usage. This positioning of the unit is firmed by means of the molded stud 71 which projects closely through a longitudinal slot 76 in the upstanding portion 68.

As is the casewith the centrally positioned wire gripping device, the wings 61 of the outer ones are supported against collapse by too much tension on the connected wire by a corresponding buttress 77 beneath them as seen best in Fig. l and this is perforated by a wire entrance opening 78 as seen in Figs. 2 and 4.

A tang 80 extends from the inner vertical edge of the upstanding section 68 and is bent at right angles to support the confronting contact 56 in position for engagement by the movable contact on the corresponding spring.

The operation of a switch of this character is well described in the aforementioned applications, it being only necessary here to point out that the depending lug 34 may engage either of the springs 41 selectively, causing it to be deflected in a direction to engage contacts 42 and 56 on one side or the other. The remaining depending lugs 32 and 33 merely act to insure separation of a previously engaged set of contacts when the knob is turned to release them, it being understood that the springs 41 are set to cause contact separation.

The wire gripping wings of the automatic devices it will be recalled have free ends, i. e., they are not connected to each other nor supported against upward movement when a wire is inserted through the opening in the bottom wall of the housing for engagement by these wings. Since the strength of the separate wings and the connecting parts in cantilever is not adequate to hold them down to insure proper grasping of the wires, a single shaped sheet of insulation 85, seen in Fig. 6, extends longitudinally of the housing and has its ends received in channels 86 in the end walls. The vertical edges of prongs 87 are engaged in slots 88 in the short vertical walls surrounding the central chamber. These prongs 87 and the corresponding ones 88 serve as holddowns for the wire gripping wings. As best seen in Fig. 1

they engage the wings only adjacent their outer bottom wall contacting edges, permitting the active inner edges to be spread by deflection of the wings by the inserted wire.

The upper tabs 90 on sheet are engaged by the undersurface of the cover to hold this sheet rigidly in position.

To permit the release of a wire after gripping by the wings, which are inclined at such an angle as to prohibit the withdrawal, unless separated, there is provided a transverse slot 32 for each of the outer wire grippers and 93 for the central one. Through a slot may be inserted the tip of a knife blade to simultaneously twist the wings thereby widening the slot between them to release the wire which may then be withdrawn. In comon the wire of more than 50 pounds without slipping or cutting of the wire.

I claim:

1. In a switch of the type described, in combination, a housing substantially rectangular in plan having an open top, a cover, a turn knob journalled in said cover and having an extension, said housing having a bottom depressed at the center to provide a deep chamber, a wire gripping terminal and contact unit in said chamber having a base secured against said bottom at one side thereof, a pair of spaced wire gripping wings upwardly inclined from their outer edges which extend transversely of said chamber and engage the said bottom, a narrow connecting portion coextensive with and between one end of each wing and the base, said portions being spaced for passage of said extension between them, the opposite ends of the wings being free, a spring arm extending upwardly from said base toward said cover and having a contact thereon facing the nearest end wall of the housing, a wire gripping unit bottomed in one depressed end of said bottom, having wings similar to those of the center unit, and an extension lying against a side wall of said housing, cooperating means on said extension and cover whereby the latter holds the last mentioned unit in position, an arm projecting from said extension carrying a contact confronting that on the spring arm, said housing bottom having a wire entrance aperture in alignment with the space between the wire gripping wings of each said unit, and means on said knob for flexing said spring arm to engage or disengage said contacts.

2. The switch as defined in claim 1 in which the free ends of the wire engaging wings are held down by straddling prongs on an insulating sheet extending longitudinally in the housing and positioned by said cover.

3. The switch as defined in claim 2 in which said prongs engage the wings only adjacent their outer edges.

4. The switch as defined in claim 1 in which said spring arm is duplicated and a second wire gripping and stationary contact carrying unit is provided adjacent the opposite end wall of the housing, said means on the knob being positioned between the ends of said springs to selectively flex one of them toward contact closing position, the springs being shaped each to bias its contact from the confronting stationary one.

5. In a switch of the type described, in combination, an open topped housing generally rectangular in plan and having a flat bottom adjacent one end thereof, a wire gripping and stationary contact carrying unit in said housing adjacent said end, said unit comprising a sheet of spring metal having a substantially flat portion extending upwardly along one side wall of said housing to the top, and a portion extending transversely across the said bottom and divided longitudinally into two freeend wings and narrower strips joining the wings to said flat portion, the side edges of said bottom portion resting on the said housing bottom, each wing being inclined upwardly from its said edges at an angle not greater than 30, a hole in said bottom directly beneath the raised edges of said wings, the narrower strips enclosing an aperture in the bottom portion, and a longitudinal slot in the upwardly extending fiat portion, studs integral with the housing extending closely through said aperture and slot to accurately position the unit in the housing and a cover for said housing adapted to engage the upper end of said fiat portion to hold the unit stationary in the housing.

6. The switch as defined in claim 5 in which an integral tang extends from the inner edge of said units upstanding flat portion normal to the plane thereof and a contact button carried by said tang facing toward the center of said housing.

7. The switch as defined in claim 5 in which a slot extends through the housing bottom adjacent the hole therein and extends transversely to the wings for the insertion of a knife blade to separate the inner edges of the wings to release a wire gripped between them and passing through said hole.

8. The switch as defined in claim 6 having a sheet of insulating material extending longitudinally of said housing normal to the bottom thereof and having prongs, one engaging each said wing near its side edge to hold that edge against said housing bottom.

9. In a switch of the type described, in combination, a housing having a separate cover, a switch operator including a knob mounted in said housing for manual partial rotation, means biasing said operator to either limit of its stroke, a pair of free-ended, facing, leaf springs cantilevered from said housing and extending adjacent the axis of knob oscillation, means on the operator to selectively move either spring in a direction away from the other, a contact carried by each leaf spring intermediate its ends and facing away from the other spring, a stationary contact supported from the base for and adjacent to each of said spring supported contacts, each of said last mentioned contacts and said springs jointly having a substantially fiat automatic wire-gripping terminal, said terminals resting against walls of said housing supporting them at levels separated from each other, each of said walls having a hole therein of only sufiicient diameter to pass a single wire to the corresponding terminal.

10. The switch as defined in claim 9 in which each stationary contacts is supported from the inner edge of a strap integral with the wire-gripper, the contact being positioned to transmit thrust to the strap in the direction of its plane and longitudinally of the housing and means on the strap and housing interlocking to resist said thrust.

11. The switch as defined in claim 10 in which the said strap is engaged by the housing cover and forced against said housing interlocking means to secure the contact rigidly in the housing.

References Cited in the file of this patent UNITED STATES PATENTS 2,206,799 Barton July 2, 1940 2,254,509 Bassett Sept. 2, 1941 2,583,756 Wahlberg Jan. 29, 1952 FOREIGN PATENTS 659,316 Great Britain Oct. 24, 1951 

